This invention relates to an improvement in multi-chambered tires of the type comprising a tubeless outer tire and a tubeless inner tire combination or assembly.
Past designs of multi-chambered tire assemblies have utilized the concept of a tire within a tire. In the event of a loss of air pressure in the outer tire, a separate inner tire or shield was provided to carry the tire's load.
The combination of inner and outer tire divided the tire assembly into outer and inner chambers, the outer chamber being the space between the radially inner surface of the outer tire and the radially outer surface of the inner tire while the inner chamber was formed by the radially inner surface of the inner tire and the rim of the wheel. The chambers were typically inflated by dual inflation valves through which air passes into the inner tire through one valve and into the outer chamber via a second valve integrally mounted on the outer tire. Alternatively air pressure can be supplied through a valve that can selectively fill the inner tire and the outer tire. In normal operation the inner tire is generally inflated to a pressure higher than the outer tire.
U.S. Pat. No. 3,219,092 relates to a dual tire as described above. The patent issued Nov. 23, 1965 to the executors of inventor Frank A. Howard.
The Howard patent describes the problem of overstretching the beads of the outer tire when attempting to mount the tire assembly on the rim. The problem was exacerbated by the inner tire flanges which necessarily increase slightly the effective diameter of the bead seat portion of the rim. The overstretching of the beads increased the risk of breakage. Howard suggested use of a very thin inner tire or redesign the inner tire using fine wires that would embed in the outer tire bead area and thus eliminate bead stretching.
An alternative to the tire assembly described in the Howard patent is a design in which the bead seat diameter of the outer tire is increased to allow for the thickness of the inner tire flanges. This design modification eliminates overstretching of the beads of the outer tire. However, a concern with this design is that if the outer tire, without the mating inner tire, is mounted on a rim, inadequate bead tension could result. The tire would be susceptible to rapid deflation due to bead unseating.
Thus, a multi-chamber dual tire should not be mountable in the absence of its inner tire.
The tension in the bead of a mounted tire must be controlled, as must the force (inflation pressure) required to seat the bead on a wheel rim. These should not be significantly increased or decreased in a multi-chamber tire as compared to the normal single-chamber tire.